1. Field of the Invention
This invention relates generally to oilfield operations and more particularly to a remotely/network-controlled additive injection system for injecting precise amounts of additives or chemicals into wellbores, wellsite hydrocarbon processing units, pipelines, and chemical processing units.
2. Background of the Art
A variety of chemicals (also referred to herein as “additives”) are often introduced into producing wells, wellsite hydrocarbon processing units, oil and gas pipelines and chemical processing units to control, among other things, corrosion, scale, paraffin, emulsion, hydrates, hydrogen sulfide, asphaltenes and formation of other harmful chemicals. In oilfield production wells, additives are usually injected through a tubing (also referred to herein as “conductor line”) that is run from the surface to a known depth. Additives are introduced in connection with electrical submersible pumps (as shown for example in U.S. Pat. No. 4,582,131 which is assigned to the assignee hereof and incorporated herein by reference) or through an auxiliary tubing associated with a power cable used with the electrical submersible pump (such as shown in U.S. Pat. No. 5,528,824 (assigned to the assignee hereof and incorporated herein by reference). Injection of additives into fluid treatment apparatus at the well site and pipelines carrying produced hydrocarbons is also known.
For oil well applications, a high pressure pump is typically used to inject an additive into the well from a source thereof at the wellsite. The pump is usually set to operate continuously at a set speed or stroke length to control the amount of the injected additive. A separate pump and an injector are typically used for each type of additive. Manifolds are sometimes used to inject additives into multiple wells; production wells are sometimes unmanned and are often located in remote areas or on substantially unmanned offshore platforms. A recent survey by Baker Hughes Incorporated of certain wellbores revealed that as many as thirty percent (30%) of the additive pumping systems at unmanned locations were either injecting incorrect amounts of the additives or were totally inoperative. Insufficient amounts of treatment additives can increase the formation of corrosion, scale, paraffins, emulsion, hydrates etc., thereby reducing hydrocarbon production, the operating life of the wellbore equipment and the life of the wellbore itself, requiring expensive rework operations or even the abandonment of the wellbore. Excessive corrosion in a pipeline, especially a subsea pipeline, can rupture the pipeline, contaminating the environment. Repairing subsea pipelines can be cost-prohibitive.
Commercially-used wellsite additive injection apparatus usually require periodic manual inspection to determine whether the additives are being dispensed correctly. It is important and economically beneficial to have additive injection systems which can supply precise amounts of additives and which systems are adapted to periodically or continuously monitor the actual amount of the additives being dispensed, determine the impact of the dispersed additives, vary the amount of dispersed additives as needed to maintain certain desired parameters of interest within their respective desired ranges or at their desired values, communicate necessary information with offsite locations and take actions based in response to commands received from such offsite locations. The system should also include self-adjustment within defined parameters. Such a system should also be developed for monitoring and controlling additive injection into multiple wells in an oilfield or into multiple wells at a wellsite, such as an offshore production platform. Manual intervention at the wellsite of the system to set the system parameters and to address other operational requirements should also be available.
The present invention addresses the above-noted problems and provides an additive injection system which dispenses precise amounts of additives, monitors the dispensed amounts, communicates with remote locations, takes corrective actions locally, and/or in response to commands received from the remote locations.